Horizon in the Middle of Nowhere

In a distant future, Japan is divided into feudal territories, which have been conquered and are ruled by outside countries. The flying city-ship Musashi, which holds the remnants of the Japanese, is being targeted and has no choice but to keep its people safe by going to war. With the fate of the world resting on its hands, the students of Musashi may hold the key to victory.

Synopsis from Anime News Network